Summary
Renewable and distributed power generation is displacing conventional base load coal and nuclear plants. This often causes large shifts in power flow during both normal and emergency operation of the transmission system. As a result, certain existing AC overhead transmission lines may exceed their design thermal rating during either normal or emergency operation.
This brochure concerns methods of increasing the thermal rating of existing overhead lines by raising the maximum temperature of the original conductor or re-conductoring the line with larger or high-temperature, low-sag conductors while avoiding the replacement or extensive reinforcement of existing transmission structures. In most applications, the line structures must be in good or excellent condition, to use these uprating methods. The existing phase conductors, however, may be replaced with High-Temperature, Low-Sag (HTLS) conductors.
If the existing line voltage is to be increased (Voltage Upgrading), other CIGRE brochures should be consulted.
Table of content
1. Rating and Uprating Overhead Lines
1.1. Key factors in line rating and uprating
1.2. Limitations on conductor operation at high temperature
1.3. TCMAX for normal and emergency line ratings
1.4. Summary of prior CIGRE conductor use surveys
1.5. Loadings, ratings, and losses
1.6. Methods of thermal uprating - Alternatives
1.7. Where high-temperature conductors apply
2. Sag-Tension at High Temperature
2.1. Sag-tension calculation method
2.2. Sag-tension corrections for high temperatures
2.3. Errors in sag calculations for multiple span line sections
2.4. “Knee-point” temperature for non-homogeneous conductors
2.5. Estimated high-temperature sag uncertainty
3. Uprating with Existing Conductors
3.1. Maintaining electrical clearances
3.2. Limiting loss of tensile strength
3.3. Avoiding connector and hardware failures
3.4. Example cases
4. Re-conductoring with Conventional Conductors
4.1. Scope
4.2. Steps
4.3. Replacement conductors
4.4. Bundling conductors
4.5. Example Cases
5. Re-conductoring with HTLS Conductors
5.1. Strand properties
5.2. Description of high temperature conductors
5.3. Re-conductoring with HTLS conductors
5.4. Example cases
6. Line Uprating Case Studies with HTLS Conductors
6.1. Theoretical re-conductoring case studies
6.2. Utility Examples of HTLS line uprating
7. Conclusion and Recommendations
8. Bibliography/References
Additional informations
| Publication type | Technical Brochures |
|---|---|
| Reference | 763 |
| Publication year | |
| Publisher | CIGRE |
| ISBN | 978-2-85873-465-8 |
| Study committees | |
| Working groups | WG B2.55 |
| File size | 8 MB |
| Pages number | 104 |
| Price for non member | 200 € |
| Price for member | Free |
Authors
D. DOUGLASS, Convenor (US), D. LOUDON, Secretary (NO)
R. STEPHEN (ZA), R. PUFFER (DE), S. UEDA (BR), K. BAKIC (SI), T. SEPPA (US), C. DO NASCIMENTO (BR), J. IGLESIAS (ES), C. BORLOT (FR), S. STEEVENS (DE), G. WATT (CA), K. YONEZAWA (JP), H. DEVE (US), J. JARDINI (BR), M. LANCASTER (US), W. CHISHOLM (CA), P. RODRIGUEZ (SP), S. KUPKE (DE), L. NAZIMEK (PL), T. KUMATA (JP), P. FIERS (AT), G. GHEORGHITA (RO), B. FIFE (US), J. DONG (US), N. HADINGER (AT), M. LEE (AU), M. BINDZAR (SK), G. BIEDENBACH (DE), T. BJARNASON (IS)
Reviewers
T. CONDON (IR), J. DOYLE (IR), P. PENSERINI (FR), P. VAN DYKE (CA), H. LUGSCHITZ (AT)
Keywords
overhead line uprating, high-temperature conductors, low-sag conductors, thermal rating, conductor replacement, line capacity increase, dynamic line rating, electrical clearance, LiDAR survey, transmission reliability
